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I W. HAHNEMANN. UNDERWATER W-AVE TELEGRAPHY.,

APPLICATION FILED JAN. 2, I

Patented May 3, 1921.

HAHNEI IANN, OE KIEL, GERMANY, ASSIGNOR TU TEE FIRM GE$ELLL$CEAET M. B. H. 0,? HEEL, GERMANY.

SIGNAL UNDERWATER WAVE TELEGBAFHY.

Specification of Letters Fatent.

Patented May 3, i921.

- Application filed January 2, 1915. Serial No. 308.

To all whom 2'25 may concern:

Be it known that I, WALTER l'lAHNE-MANN, a subject of the Emperor of Germany, and residing at Kitzeberg, b /Kiel, c/o Signal (iesellschaft m. b. H. Kiel, lVerlr Ravensber g, Germany, have invented certain new and useful Improvements in Underwater Wave Telegraphy, of -which the following is a specification.

This invention appertains to trans-marine radiotelegraphy, and one object of the same is to provide a system of trans-marine radiotelegraphy which may be employed on stations one or both ot'which are located on shore or on shipsat sea, wherein the elements employed for radiating the electrical energy are disposed below the surface of the water, and the radiotelegram transmitted through the latter.

Another and further object oi this invention is toprovide a system of trans-marine radiotclegraphy which is particularly applicable to naval vessels inasmuch as the elements for radiating the electrical energy are disposed below the surface of the water and consequently are not exposed to destruction when said vessels are involved in a naval engagement.

Another and still. further obj ect of this invention is to reduce the cost of constructing a radiotelegraph station by eliminating the extremely high aerial towers now employed and substitute the underwater radiating elements proposed by this invention.

Another and further object of this invention is to provide a system wherein the possibility of a vessel having its radio system crippled by reason of damage to aerial is reduced-to a minimum.

With these and other objects in View, my

invention consists of certain novel features of construction, combination and arrangement of parts to be hereinafter set forth and claimed.

In the accompanying drawings Figure 1 represents a portion of a ship partly in section showing a high frequency transmitter mounted thereon;

Fig. 2 is a similar view showing a receiver;

Fig. 3 is a diagrammatic view showing the dissemination of the electric waves in the water.

Heretofore it has been customary in sys toms of radiotelegraphy to have the eleccnsequently comparatively free from de-' Now it is to eliminate the various disadvantages heretofore mentioned with respect to the trans-marine radiotelegraphy systems now in use, and to provide a system in which the elements employed for radiating or collecting the radiated electrical energy, in other words, the antenna is disposed below the surface of the water and struction, which thus makes it impossible to cripple the system by damage to the antenna.

The difiiculty however, which up to the present has prevented the practical use of underwater radiotelegraphy has been due to the fact that the usual frequencies of the electrical source utilized in connection with the ordinary systems of radiotelegraphy cannot overcome the ohmic resistance of the sea water, furthermore it is a well known principle of radiotelegraphy that the relation of the ohmic resistance to the capacity reactance plays a part in so far as with the rising frequency in general the valueof the relation of the latter with respect 'to,.the ohmic resistance sinks. If therefore it is possible to make the capacity reactance equal to or smaller than the-ohmic resistance then communication under water by means of electrical waves is possible.

It will thus be seen..that by an increase in.

the current frequency it is possible to diminish the reactance of the conductin me- As the losses of energy in case of dielec-a trictransmission for the above mentioned reason is considerably lessened, then in case of transmission by pure current conductioni a considerable increase in range is obtaine presupposing that success is obtained in radiating considerable quantities of energy in the form of very short waves.

The gist of this invention resides in the fact that the frequency of the electric current is so calculated that the reactance of the medium, that is the sea water, becomes equal to or less than the ohmic resistance of the medium. This requirement is obtained owing to the fact that the frequency adopted for use is selected at not less than 3X10, vibrations ilf'a second because as calculation shows, at this frequenc the specific resistance is already approximately equal to the,

sible to transmit radiotelegrams through the water as they are now transmitted through the air. The generator to produce proper results must, it is found, produce a current having a frequency greater than 3X10 per second. In this connection it is to be understood that the radio energy is transmitted to the water by suitable radiating elements arranged for instance on the bottom of the ship, while on the receiving station, which may be another ship, a corresponding receiveris arranged, which absorbs the radio waves and transmits them to a detector suitable for frequencies of the above mentioned magnitude.

In the embodiment illustrated, an arrangement for practically carrying out the invention is shown which includes a trans mitter which is'housed in the double bottom of a ship preferably between two beams A, and comprises two radiators O, 0 formed in accordance with the known Hertz oscillators having one of their ends thereof disposed in a receiver B filled for instance with petroleum P and with their other ends extending into 'the water outside. v The oscillators O are connected to the generator G by the leading in or conducting wires Z which pass through the ships bottom W and are surrounded by suitable. insulation at their points of passage through the bottom. Between the radiators' O, O which serve as electrodes, there passes a luminous are which generates very high frequency waves after The receiving device shown in Fig. 2 is similar to the transmitter and has disposed below the bottom of the ship W electrodes E similar to the oscillators of the transmitter. These electrodes have one of their ends disposed in a receiver B secured to the bottom of the ship and filled with petroleum P while their other ends project into the water. Between the ends of the electrodes E which are arranged in the petroleum receiver there is rovided a thermoelement T connected wit a galvanometer M by the conductors Z which extend through the ships bottom and have insulating material arranged around them at the points where they pass through said bottom.

It is to be understood that both the transmitter and the receiver may be arranged on the same ship if desired as is shown diagrammatically in Fig. 3. The waves V sent out-from the transmitter O- spread out into the water in the form shown in Fig. 3 and as soon as they reach the receiver E may be recognized by the deviation of the galvanometer connected with it.

The principle upon which this invention operates may be more readily understood by referring to the Ohm s law for alternating current which is represented as follows:

x/W +(w I? In this equation denotes the impedance which a tension E has to overcome to produce a current J. The

value to is the product of 21: and the number .115

n of quiet oscillations per second. If the conducting path is of such a nature that the current does not produce a magnetic field,

then L will be zero.

However, if the conducting ath is of 20 such a nature that no amount of electricity can remain quiet upon it, then C, the capacity, is equal to zero. That is to say, the

conducting path is capacity free. In these cases the values 'wL and of which the first means the inductance caused by self-induction, while the latter denotes the reactance caused by capacity can be considered fallen away or disappeared. V The self-induction L and consequently the value wL of the fore going equation does not now come into question. The ohmic resistance WV is, as is apparent from the equation, absolutely independent of the value :21m of the alternating current. The reactance of the the equation however, which as stated above,

' also possesses the characteristics of a resistance, is directly dependent upon the magnitude of the capacity Gas well as upon the magnitude of the value W and in such a manner that this value will become less when the capacity increases and also when the frequency rises. In the above cited example it will be seen that we only have to observe now in which the values W and 100 remain constant. If one now considers the relation of the values N and w(), it will be found that falls with the rising W the value of '75 value of w. Obviously, one can consider in a conducting medium capable of great allaround expansion in all directions and a high dielectric constant, that an alternating current can be divided into two currents, one of which is propagated through ordinary conduction while the other would propagate itself similar to the manner in which/ an alternating current would pass through a condenser filled with an insulator. first named current the value W is con trolling for the magnitude of resistance, and for the last named current it is controlling for the value In w=. 21m=O, the

value becomes infinite. It will thus be seen that with a very high a and also a very high '11) the value of when compared with the value W is very small.

For the It naturally follows that in a rising frequency more and more current must spread out on the last mentioned path and further- However, inasmuch as the capacity reactance of the transmitting ohmic resistance of said medium.

2. A system of submarine radiotelegraphy having high-frequency transmitting and receiving elements disposed beneath the surface of the water, and utilizing an alternating current of such frequency as to cause the capacity reactance of the transmitting medium to be smaller than the, ohmic resistance of the medium.

3. A system of submarine radiotelegraphy medium at its highest to be equal to the having high-frequency transmitting and receiving elements disposed beneath the surface of the water; and utilizing an alternating current having a frequency of at least 3X10 per secon'rl.

4. A system of submarine radiotelegraphy having high-frequency transmitting and receiving elements beneath the surface of the water and utilizing an alternating current having a frequency of more than 3 10 1 per second.

In testimony whereof I ailix my signature in presence of two w1tnesses.

- WALTER MAHNEMANN';

Witnesses Jumus Rornn, HUGO LIGHELT. 

